Over the years and in accordance with anti-pollution regulations and clean air standards, vapor recovery systems have become important features of fuel dispensing systems. Many fueling systems now include vapor recovery systems that include vapor recovery lines disposed between the fuel dispensing nozzles of fuel dispensing systems and the fuel storage tanks, typically disposed underground, from which storage tank fuel is drawn for dispensing through the fuel pump and the fuel dispensing nozzle. The systems are typically designed to provide for the recovery of fuel vapors and the return of such vapors through the vapor recovery line to the fuel storage tank.
It is considered desirable to be able to monitor the flow and flow rate of the fuel vapor being returned to the fuel storage tank through the vapor recovery line. Prior devices that might serve such purpose have suffered from a variety of shortcomings, as a consequence of which there has remained a desire for an improvement in the vapor recovery line that will allow the flow and flow rate of fuel vapor being returned to the fuel storage tank to be monitored.
To address such desire, an improvement in the vapor recovery line has now been developed that includes a vortex shedding vapor recovery line flow meter that is installable between an upstream portion and a downstream portion of the vapor recovery line.
In recent years it has been found that the flow and flow rate of fluids can be measured by utilizing vortex shedding techniques and by subjecting the resultant vortices to sonic transmissions. In general, a vortex type meter makes use of a non-streamlined strut or other vortex generating device in the flow stream. As the flow passes such strut or other vortex generating device, vortices are formed and are shed behind the strut or other vortex generating device, with the number of vortices shed per unit of time being proportional to the flow rate. Typically, an ultrasonic beam is then positioned downstream in the flow stream a short distance and such beam intercepts the vortices as they pass, resulting in detectable modulation of the beam signal.
Descriptions of several such flow meters and related components and discussions of the techniques associated therewith may be found in Joy et al U.S. Pat. No. 3,680,375; Colton U.S. Pat. No. 4,031,757; Joy et al U.S. Pat. No. 4,240,299; Mahanny et al U.S. Pat. No. 4,312,236; Thorne et al U.S. Pat. No. 4,312,237; Johnson U.S. Pat. No. 4,424,714; and Joy U.S. Pat. No. 4,437,349.
Such vortex shedding flow meters typically effect sine wave type outputs, with the frequency of the sine wave being approximately proportional to the volumetric flow rate of the gas or other liquid and independent of the composition of the gas or liquid.
Applicant has determined that such techniques are adaptable for use in flow meters that are installable within vapor recovery lines and has now developed an improvement in a vapor recovery line that includes a vortex shedding flow meter that facilitates the measurement of flow and the flow rate of vapors within the vapor recovery line and that is conveniently comprised within a housing particularly adapted and configured for installation within such vapor recovery lines.